Recently, a radiation imaging apparatus using a flat panel detector (FPD) formed of semiconductor material has began to be in a practical use as an imaging apparatus used for medical image diagnostics and non-destructive inspection through an X-ray. Such a radiation imaging apparatus is used as a digital imaging apparatus for still image radiographing such as radiographing and moving image radiographing such as fluoroscopic radiographing, for example, in medical image diagnostics.
Regarding such a radiation imaging apparatus, as disclosed in Japanese Patent Application Laid-Open No. H11-128213, it is considered that an area where an FPD reads out (field size) may be switched to and from an X-ray irradiation area. However, if the irradiation area becomes wider after switching, pixel sensitivity or an dark output differs between in an area irradiated and in an area not irradiated in the FPD. Therefore, a ghost (step of image) affected by the irradiation area occurs in a provided image, which may cause image quality degradation.
Japanese Patent Application Laid-Open No. 2008-167846 considers that image processing may be carried out for correcting a ghost affected by such a changing in irradiation area. Specifically, a ghost correction factor is derived, based on data having a ghost according to uniform irradiation for each of X-ray irradiation conditions. Based on the ghost correction factor, a required ghost correction factor is derived that corresponds to an X-ray irradiation condition at collecting data about an object portion to be inspected, i.e. an irradiation area, and time from the start of X-ray irradiation. Thus, the data about the object portion to be inspected is corrected by using the required ghost correction factor to create corrected image data.